I can break into that spot easily. And I know of a few other regulars who can too.
All you need to do is get one or two zombies, stand on their head, and push E on the barrel through the wall. It'll push it in, and then a zombie can walk in and jump over it (or if they shoot the barrel into the zombie it's even easier because the zombie can just glitch through it once inside) and tag the guy(s) in there.
Agreed.